


Unintentional Voyeurism

by Vienamarie



Category: Undertale (Video Game)
Genre: M/M
Language: English
Status: Completed
Published: 2016-06-19
Updated: 2016-06-19
Packaged: 2018-07-15 22:27:20
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,372
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7241275
Author URL: https://archiveofourown.org/users/Vienamarie/pseuds/Vienamarie
Summary: <blockquote class="userstuff">
              <p>When Undyne visits the skeleton brothers to surprise Papyrus with an impromptu cooking lesson, she gets more than she bargained for.</p>
            </blockquote>





	Unintentional Voyeurism

Undyne was a clever fish monster.

The captain of the Royal Guard considered herself a very formidable threat under the right circumstances. She was fast, strong, intelligent, and stealthy. At the moment, she was hiding out in the closet of Papyrus’ bedroom, waiting for him to come home so she could jump out and surprise suplex him, then wrassle the skeleton into a last-minute cooking lesson. Her house had just been rebuilt, and her oven could withstand more than six hundred degrees without blowing up this time! The sound of the front door opening knocked her from her thoughts and made her sit still amongst his closet of clothes and action figures. 

When his bedroom door opened, she very nearly pounced out and tackled him, but some very recognizable sounds made her freeze up. 

Groaning. Papyrus was groaning, and it wasn't from pain. There was a second voice with him, distinctly male (damn, she owed Alphys 20G), and her cold-blooded body turned to ice as she recognized it as Sans’. 

Was she being punked? This couldn't be real. No way was this happening!

The closet had thin slits in the door, allowing her to see a little of what was going on, much to her chagrin. Papyrus had pinned Sans against the wall and forced his jacket off, their teeth and tongues colliding in a heated kiss as the shorter brother tugged at his brother’s battle body. 

By the grace of Asgore, the skeleton brothers were skeleton lovers.

“Been waitin’ for this all day.’ Sans panted when they parted, half-lidded eyes meeting Papyrus’. “You really should consider wearing more than blue speedos, you know. Putting on quite a show for onlookers every day.”

“Rubbish, brother.” Papyrus grinned, and Undyne doesn't think she's ever heard him sound like that before. Quiet, and lusty. She thought he was just a little dense to be sexual like this but unfortunately she was being proved very, very wrong in the very, very worst way. On the other hand, Sans has never been this visually responsive to anything as long as she’s known him. “Don't pretend the sight doesn't please you.”

“Fuck, it does.” Sans agreed, unable to refute it. They'd ditched their shoes and other excess clothing on the ground, the duo nearly stumbling over Papyrus’ signature red scarf as they worked their way to the bed. “You'd look a lot better without them on.”

“I could say the same thing to you, brother.” Papyrus answered, pointedly tugging on Sans’ shorts. The shorter male got the message and discarded them the same time Papyrus removed his own bottoms, leaving each of them in their tops. Too eager to bother taking those off, too, Sans was lifted up and unceremoniously dumped onto the mattress of his brother’s race car bed, pinned by the male’s larger body. “You look wonderful beneath me, Sans.”

Undyne could see blue painting Sans’ face. He shifted and chuckled. “Always a charmer, bro. Why give each other compliments when we could use our mouths for something better?”

Oh god. They were very passionately making out on Papyrus’ bed, and Undyne could hear and see it all. She wanted to run out of the closet and dunk her head in a bucket of ice water in the hopes of calming her heated face, but she couldn’t leave without being caught. She was screwed, and she had to stay there and listen to them screw. What deity had she pissed off to deserve this!? She would punch them in revenge, she's sure.

How long had they been together like this, Undyne wondered? In front of others they acted like they usually do; brotherly, and nothing more. But clearly that wasn't the case. She could understand why they were keeping it secret, though; sexuality didn't matter to monsters, whether you were hetero, homo, ace, whatever, but even incest was a little taboo. Sans and Papyrus probably had to tiptoe around their love a lot, and she felt guilty.

She loved them like they were her own siblings. And hell, if they chose to love each other in every sense of the word, and as long as neither got hurt, she would support them.

But that didn't mean she needed to witness them doing the do. At one point she had jokingly wondered how skeletons could have sex, but now she was going to find out. 

Damn, today was a bad day to hide in Papyrus’ closet.

“Ah, Pap!” Sans cried, startling Undyne out of her thoughts. Papyrus had his fingers inside Sans’ ribcage, lightly scraping and groping the bones to elicit a response from his brother. The smaller skeleton writhed beneath him, scrambling for any kind of purchase. He found it in Papyrus’ pelvis, rubbing the bone with practiced ease. The taller of the two groaned and bucked into his hands, panting softly.

“Sans…” He moaned, needy and affectionate. “I...I need…”

“I got ya.” Sans breathed, sitting up slightly. “Come here.”

Papyrus crawled into his older brother’s lap, circling his arms around his neck and engaging in another heated kiss while Sans dipped his fingers beneath the other male’s battle body and caressed his ribcage. It was sweet, Undyne couldn't help but think, as she was forced to accept her fate of being stuck in this damned closet to watch them be together. The brothers had started out in a passionate craze, but now they were being soft, intimate. The fish monster smiled a little, hugging her knees to her chest as her thoughts briefly drifted to a certain yellow lizard. 

Sans broke the kiss to pull Papyrus’ top off, leaving him completely bare to him. Papyrus did the same to Sans, his shirt joining the rest of their clothes on the floor. Both of their chests were glowing, souls ready to emerge and interact with each other.

“Remember to breathe.” Sans told his brother with a quiet fondness that wasn't there a moment ago, thumbs brushing over his pelvis. “Tell me if you need to stop.”

“Sans, we do this every time.” Papyrus grinned, just as soft. “Make love to me, brother.”

The older of the two didn't need any further encouragement. Their souls manifested as they shared another kiss, moaning simultaneously as they collided and brushed against one another. 

They were soul to soul, chest to chest, desperate for the close contact yet craving more. Papyrus grew greedy and forced Sans to lie down, kneeling possessively overtop him and grinding their hips together. Sans whimpered, bucking up to meet him and panting. The room was filled with their heavy breathing and fluctuating magic. Their souls rubbed together at a more frantic pace and Papyrus was practically rutting Sans into the mattress, pinning his hands down on either side of his head. Sans didn't seem to mind, mumbling praises to his brother.

“Nng...s-so good, Pap...fuck, that feels great…” He said. “You're doing so good...hff...you're so beautiful.” Papyrus was blushing and Undyne had long stopped trying to cover her ears, unable to block out the sounds of their passion. This was something she wasn't meant to see, something special between them. She felt equal parts guilty and embarrassed. As soon as they were distracted enough, she was going to hightail it outta there.

Their breathing grew into loud sighs and moans, bodies so close together neither could tell where one brother ended and the other began. Papyrus’ eyes were closed in euphoria, his expression one of the greatest things Sans has ever seen. He leaned up to kiss him again, their ribcages pressed so tightly together it forced them to breathe in unison. 

They were getting close. Sans could feel it in the way Papyrus was thrusting himself against him in a rushed, jerky manner. Their bodies collided again and again with delicious friction, blue and orange magic occasionally flickering around them as their orgasms drew near.

“S-Sans!” Papyrus whimpered. “Sans, I'm gonna-”

“D-do it.” The older male panted. He nipped encouragingly at Papyrus’ clavicles. “Cum for me. Let it go, Pap.”

That was all the encouragement he needed. Papyrus thrusted against him thrice more before going rigid. His soul glowed almost blindingly bright and his brother’s name left his lips in a desperate mantra as he climaxed. Overwhelmed by it all, Sans came immediately after. His soul pulsated against Papyrus’ and heated whines left his mouth. 

Sans went limp and became a trembling mess of bones beneath Papyrus. His brother collapsed beside him in a similar condition, barely having the strength to tug the blanket over their bodies before drawing the smaller skeleton close to his chest. For a while, nothing could be heard but their slightly labored breathing, and Undyne thought they might have fallen asleep. Unfortunately, Papyrus’ voice proved her wrong.

“We should probably shower, brother. That was a very physically taxing activity and we are both gross and sweaty.”

“Mmm...nah, bro.” Sans mumbled. He sounded like he was ready to pass out. “Let's nap first. Then shower.”

“Sans, you lazybones!” Papyrus was back to his usual speaking tone. “Besides, I'm hungry now. I think we could both use a delicious plate of spaghetti!”

“Can you bring it to me?”

“Saaans!”

Papyrus sat up in the bed, full of energy like he hadn’t just fucked Sans into the mattress. “Don't go to sleep! I'll carry you into the shower if I have to!”

Sans just weakly raised his arms in the universal “pick me up” motion, making his brother sigh. He could tell he wasn't annoyed, however, given that he was trying to hide a smile.

“You're hopeless.” Papyrus scolded, getting out of bed and taking Sans into his arms. 

“But you love me anyway.”

“Yes, I do.” He kissed Sans on the forehead and the shorter skeleton grinned. They left the room together and Undyne let out a sigh of relief. Once she heard the shower running, she crept out of the room and downstairs, then left the house and took off in a sprint for Waterfall. This encounter would never leave her mind, ugh!

\\\\\

“Papyrus should be out in a minute.” Sans said to the fish monster a week later. She entered the correct way this time - kicking the front door down instead of sneaking in to hide, and Sans was the only one in the living room. “As soon as he finishes reorganizing his action figures he'll come down.”

“Lucky for him I'm THE MASTER of patience!” She exclaimed, plopping down on the couch and propping her feet up in Sans’ lap. “So what's new with you, punk? Find any new places to nap on the job?”

“Papyrus’ bed is pretty comfy.” He said, and the woman froze momentarily. 

“Heh...what?” She said, brushing it off. There's no way he knew. She was so stealthy!

“I know you were there.” Welp, there goes that. The atmosphere in the room was tense, almost suffocating as she waited for his next words.

He was looking at her now, his eyes doing that freaky thing she hated where he didn't have any pupils, just pits of black. The fact that he was doing it at her made it all the more intimidating. She took her legs off his lap and sat up.

“Sans-”

“I didn't find out until after the fact.” He said. “Papyrus thought he had left his closet open, but he doesn't do that. After the shower he even picked up our clothes and vacuumed the floor. So I snuck a peak inside the closet and what did I happen upon?”

He took his hand out of his pocket to show her a lone, red hair.

“You can see how I put two and two together, considering we don't have hair.” He said. “So what do you want, Undyne? What's it gonna take for me to buy your silence?”

“...what?” She said, blinking. Undyne was expecting him to go off on her for invading their privacy, to use his blasters to dust her or threaten her to stay away from them, anything but whatever this was! “What do you mean?”

“What do you want?” He repeated. “Money? A favor, how do I keep you from letting this out?” His eyes were back again, but they were dim, and his expression was strained. He looked...nervous? No.

He looked afraid. And suddenly she understood why.

“Sans, I'm not gonna hold this over your head.” She stated seriously.

“Why wouldn’t you?” he challenged. “I'm...Undyne, this isn't exactly a social norm. Papyrus has a hard enough time trying to make friends as it is, but if anybody found out he was having sex with his brother? He'd-”

“You don't want to see him get hurt.” She interrupted. “I get it, punk. I don't, either. You two are like weird brothers to me, too. Whatever you two do with each other...really isn't my business. I wasn't supposed to find out; that was a total accident. But I'm not gonna hold it over your head!” Undyne leapt up and placed her hands on her hips, staring at him with her good eye. “I'm a soldier! I've got integrity and honor!! Blabbing your secret out of spite or opposition is downright COWARDLY!!” She calmed down again and sighed. “You...you can trust me. I'm sorry I made you worry otherwise. Whatever reasons you have to hide this are probably good ones, anyway, right? I'd never intentionally hurt you guys.”

Sans stared at her hard, the two lapsing into silence for a while. Then he relaxed, and smiled. “Okay, Papyrus. You can come down now.”

The taller skeleton let out a squeal and bounded down the stairs to grab Undyne up in a hug, effectively crushing the air from her lungs. “I'm so happy you aren't a threat to our happiness!!” He exclaimed. “You're a very supportive best friend, Undyne!”

The blue fish grinned and hugged him back. “Heh, I support whatever makes ya happy, punk! Now c’mere!” She broke out of the embrace and spun him around, wrapping her arms around his waist and suplexing him into the coffee table. “WE’VE GOT A COOKING LESSON TO GET TO!! MY OVEN CAN GO HOTTER THAN SIX HUNDRED DEGREES, NOW!!”

“Wowie!!”


End file.
